How do I get more male flowers on my zucchini plants?
I asked this question last May or June before planting. Stephen Brown suggested I get the soil sampled to check for a nutrient deficiency. I did fairly cheap sampling but found my soil to be high in nitrogen & phosphorous and low in potassium. Blossom end rot later suggested low calcium content as well. I fertilized accordingly. Proper fertilizer definitely kept the plants and fruits healthy, but I doubt it made the difference in male flowers. This was the hottest summer in my memory in the Mat-Su Valley. I had plenty of male flowers for the first time in years. As soon as the weather finally cooled off in September, the plants stopped producing male flowers. It was quite sudden. New flower buds produced during cool periods were all female. Male buds showed up only on hot days. During the cool period in September and October, many male flowers had bare, stunted anthers - no pollen.
I've read that high temperatures can result in too many male flowers. I hypothesize that cool temperatures stop the plant from producing them. I never set up a greenhouse for a proper experiment this year because the weather was so hot. If next summer is more normal, I will try it then. Perhaps some other high latitude gardeners will experiment with this as well?
Matanuska-Susitna Borough Alaska
I think your observations are correct. I would add that high nitrogen in the presence of high heat might also contribute to few female flowers.